Project Summary In the United States, 1 in 13 children are affected by a communication disorder. While behavioral indicators of communication, language, and associated disorders can be observed in the first year of life, diagnosis often cannot be made until after the second or third year. By that point, developmental trajectories may have begun to diverge off course with lifelong, cascading consequences. There is a need for interventions that may be implemented in infancy, a time of enhanced neuroplasticity and emerging foundational skills, in order to prevent full manifestation or exacerbation of communication delays and to promote healthy communication development. Although short-term experimental interventions have positively impacted skills in infant communication (including social, nonverbal, and verbal components), real-world enrichment programs appropriate for infants and tailored for communication development are not available. Successful interventions targeting communication delay and disorder implemented in the second year and beyond cannot be presumed to be appropriate for use in infancy. Thus, we propose a novel communication-targeted preventive intervention, Infant Achievements (IA), for infants at high risk for communication delays. Specific aims are to: (1) assess effects of the IA intervention on caregiver's implementation of targeted child development-enhancing strategies; (2) assess effects of the IA intervention on child communication development; and (3) examine the relation between caregiver fidelity and child outcomes. Participants will be randomized to one of two 8-week in- home treatment conditions: IA (with twice-weekly caregiver coaching) or Caregiver Education (CE) comparison condition (no caregiver coaching). The short-term intervention period is intended to enhance intervention efficiency and permit examination of specific mechanisms of change. Caregivers in the IA group will be trained in the use of communication-supporting strategies adapted from naturalistic developmental behavioral interventions, implemented during joint-action routines supported by the use of innovative strategically- designed toy bundles and user guides. These toy bundles provide the exostructure for the intervention, easing caregiver learning demands and promoting generalization. Caregivers in the CE group will receive weekly in- home Child Development Tutorials plus weekly phone follow-up and toys differing from IA toy bundles. Rigor is attained via a randomized controlled trial (RCT), strong counterfactual, use of targeted and valid measures, fidelity measures, blinding of examiners and coders, and focus on targeted outcomes using dense observation of child and caregiver behaviors. Caregiver and infant outcomes will be assessed pre- and post-intervention, at a 2-month follow-up, and during the intervention. Long-term goals include refining the IA intervention, as needed, examining its efficacy for infants and caregivers in a larger RCT, and examining mediators of treatment response in caregivers and infants.